基于激发态分子内质子转移（ESIPT）和聚集诱导发光（AIE）活性的菲并咪唑Fe3+荧光探针及细胞成像研究

An Excited-State Intramolecular Proton Transfer（ESIPT） Plus Aggregation Induced Emission（AIE） Phenanthro[9,10-d]imidazole-Based Fluorescence Probe for Detection of Fe3+ in Living Cells

设计合成具有激发态分子内质子转移(ESIPT)和聚集诱导发光(AIE)特征的酚羟基菲并咪唑Fe^3+荧光探针PIP-o-OH,对其结构进行了表征和确认,并通过单晶结构确认了探针PIP-o-OH中的O-H与咪唑N的分子内氢键.紫外和荧光光谱分析表明,探针PIP-o-OH与Fe^3+形成络合物后实现Fe^3+的选择性识别,并通过质谱和离散傅立叶变换(DFT)计算确定了探针PIP-o-OH与Fe^3+的配位方式.探针PIP-o-OH与Fe^3+络合前后的荧光变化成功应用于HeLa细胞和实际水样中Fe^3+的检测.

Selective detection of Fe^3+ has considerable importance due to its active involvement in various biological processes. Based on the mechanism of excited-state intramolecular proton transfer(ESIPT) plus aggregation induced emission(AIE), a fluorescence probe of phenanthro[9,10-d]imidazole modified by the phenolic hydroxyl(PIP-o-OH) had been designed, synthesized and applied in the detection of Fe^3+. The structure of PIP-o-OH was characterized by 1H NMR, 13C NMR, IR, HRMS and X-ray single diffraction. Furthermore, a clear intramolecular hydrogen bond was observed between hydroxyl O-H and imidazole N atom in X-ray single structure, which improved the impossibility of ESIPT activity. ESIPT and AIE activities of PIP-o-OH were adequately determined by absorption, emission spectra and scanning electron microscope(SEM). The aggregated PIP-o-OH in MeOH/H2O(V:V=1:9, Hepes 10 μmol/L, pH=7.4) exhibited a good sensitivity towards Fe^3+ with "turn-off" fluorescence response just after 20 s. The limit of detection(LOD) was calculated as low as 0.49 μmol/L. So it could be utilized to detect Fe^3+ in biology and environmental samples. In addition, the calculation of the density functional theory(DFT) confirmed the formation of PIP-o-OH-Fe^3+ complex. Also, PIP-o-OH was successfully applied to monitor Fe^3+ in HeLa cells by the fluorescence change and quantificationally detect Fe^3+ in water samples.